The present invention relates to an electric power and communications signal distribution unit, particularly suitable to be used in combination weighers to connect and power the individual heads.
The combination weighers to which the invention relates are constituted by a plurality of independent weighing stations, known as heads, which are connected to a so-called central control unit, constituted by a PC or the like, by way of a communications network.
Each head, with reference to its mechanical structure, has its own vibrating channel, a loading bucket, a weighing bucket coupled to a load cell or the like and an optional memory bucket.
The vibrating channel is normally actuated by an electromagnet, while the buckets are provided with shutters moved by step motors.
In a typical embodiment of a combination weighing system, the heads are arranged in a circular configuration, so that the product to be weighed can slide radially from the center, where there is an upper cone, toward the heads and then from these heads toward a transfer device, for example a cone or funnel, which conveys the weighed product toward a packaging system.
The methods most widely used to control the electromechanical and electronic components of the heads of a combination weighing system are essentially two.
According to a first method, also known as functional approach, a plurality of control units (electronic boards) are provided, each being designed to manage a specific function (for example control of all the motors, control of all the electromagnets, et cetera).
This method has several drawbacks.
First of all, a fault of a single board compromises the operation of the entire weigher, since it compromises the management of the components that the board controls and drives.
In each head, which is identical to all the others, there is one of these components, and therefore the operation of all the heads is compromised.
Moreover, it is necessary to lead cables from each control unit in order to wire the controlled component in each head.
This entails a very complex wiring, which must be performed by highly specialized personnel in order to avoid incorrect connections.
The second known method, known as modular approach, entails that each head is provided with a control unit (an electronic board that manages only the electromechanical and electronic components of the head being considered).
This method is certainly better than the functional approach method.
First of all, it allows to have heads that are totally independent from the standpoint of power supply and control, thus simplifying construction and achieving the advantage that a fault of a single board compromises the operation of a single head, while all the other heads can continue to operate without problems.
The modular approach method also allows to provide more efficient wiring inside the machine.
The heads become true electromechanical modules, which are powered by a single electrical power supply system and are driven by the central control unit over the communications network.
In this case, the number of wires is reduced considerably with respect to the case of the functional approach, and construction, technical support and maintenance of the system are thus simplified.
Even in the case of the modular approach, however, there are problems in the electrical wiring for supplying power to the electronic boards of each head starting from the transformers located inside the machine and for creating a communications network between the boards and the central control unit.
The problem, according to the background art, has been solved partially by central-symmetry distribution systems, designed to supply power to the heads and allow them to communicate with the central control unit.
These structures have a cylindrical shape or are monolithic prisms that have as many faces as there are weigher heads to be served.
Considering schematically the body of a combination weigher as a metal cylinder with lateral openings in which the weighing heads are inserted, these distribution systems are placed at the center of the cylinder.
Their structure is based on a plurality of self-centering connectors, which are mounted vertically on the faces of the distribution prism and allow engagement with the heads when the heads are inserted radially in the body of the weigher.
The heads of the weigher must be provided with self-centering connectors that are complementary to the connectors of the distribution system.
The disadvantages of these structures are first of all related to the high cost that arises from the use of special self-centering connectors and most of all from the difficulty of assembling and wiring these connectors to the entire system.
The wiring requires complex assembly procedures and still requires the manual skill of expert operators, but despite this the connections can be unreliable and difficult to maintain indeed because they are structurally complicated.
The aim of the present invention is to overcome the problems of known distribution units by providing a distribution unit that in particular is easy to manufacture.
Within this aim, an object of the invention is to provide a distribution unit that substantially eliminates wiring problems.
Another object is to provide a distribution unit in which the remaining wiring can be provided even by a person who is not particularly specialized.
Another object is to provide a distribution unit that uses low-cost components.
Another object is to provide a distribution unit in which maintenance operations are simplified.
This aim and these and other objects that will become better apparent hereinafter are achieved by a distribution unit for electric power and communications signals, particularly for heads of combination weighers, characterized in that it comprises a flexible printed circuit provided with a plurality of multipole connectors, at least one for each head of the machine, said flexible circuit being mounted on a substantially cylindrical supporting structure arranged at a center of a combination weigher, said circuit carrying, by means of a plurality of electrically conducting tracks, an electric power supply and electronic communications to complementary multipole connectors provided in electronic boards of all weighing heads.